Of current communications networks, second-generation (2G) networks such as Global System for Mobile Communications (GSM) networks, and third-generation (3G) networks such as Wideband Code Division Multiple Access (WCDMA) networks have separately provided full coverage. As network technologies of Long Term Evolution (LTE) develop, LTE networks have begun to cover traffic hot spot regions, and coexist with the GSM networks or the WCDMA networks.
When initiating or performing a circuit switched (CS) service, user equipment (UE) on an LTE network may fallback from the LTE network to a 2G network or a 3G network to continue to complete processing of the CS service. This technology is also referred to as circuit switched fallback (CSFB), and enables a network device on a 2G network or a 3G network to be reused to provide a conventional CS service for UE on an LTE network. UE may choose to fall back from an LTE network to a 2G network or a 3G network in multiple manners, for example, a redirection-based manner, a PS handover-based manner, or a single radio voice call continuity (SRVCC) handover-based manner.
When a serving cell of UE is handed over on an LTE network, the UE needs to exchange signaling with a network device such as an MME or an eNodeB for multiple times. In the prior art, if UE initiates, in a serving cell handover process, a voice service and triggers a network device such as an MME or an eNodeB to implement CSFB, the network device chooses to implement the serving cell handover process. As a result, the voice service initiated by the UE cannot be successfully established.